This invention relates generally to molecular detection and analysis, and more particularly relates to configurations for a nanopore arranged to detect molecules translocating through the nanopore.
The detection, characterization, identification, and sequencing of molecules, including biomolecules, e.g., polynucleotides such as the biopolymer nucleic acid molecules DNA, RNA, and peptide nucleic acid (PNA), as well as proteins, and other biological molecules, is an important and expanding field of research. There is currently a great need for processes that can determine the hybridization state, configuration, monomer stacking, and sequence of polymer molecules in a rapid, reliable, and inexpensive manner. Advances in polymer synthesis and fabrication and advances in biological development and medicine, particularly in the area of gene therapy, development of new pharmaceuticals, and matching of appropriate therapy to patient, are in large part dependent on such processes.
In one process for molecular analysis, it has been shown that molecules such as nucleic acids and proteins can be transported through a natural or solid-state nano-scale pore, or nanopore, and that characteristics of the molecule, including its identification, its state of hybridization, its interaction with other molecules, and its sequence, i.e., the linear order of the monomers of which a polymer is composed, can be discerned by and during transport through the nanopore. Transport of a molecule through a nanopore can be accomplished by, e.g., electrophoresis, or other translocation mechanism.
In one particularly popular configuration for molecular analysis with a nanopore, the flow of ionic current through a nanopore is monitored as a liquid ionic solution, and molecules to be studied that are provided in the solution, traverse the nanopore. As molecules in the ionic solution translocate through the nanopore, the molecules at least partially block flow of the liquid solution, and the ions in the solution, through the nanopore. This blockage of ionic solution can be detected as a reduction in measured ionic current through the nanopore. With a configuration that imposes single-molecule traversal of the nanopore, this ionic blockage measurement technique has been demonstrated to successfully detect individual molecular nanopore translocation events.
Ideally, this ionic blockage measurement technique for molecular analysis, like others that have been proposed, should enable molecular characterization with high sensitivity and resolution on the scale of single monomer resolution. Unambiguous resolution of individual monomer characteristics is critical for reliable applications such as biomolecular sequencing applications. But this capability has been difficult to achieve in practice, particularly for solid-state nanopore configurations. It has been found that the length of a solid state nanopore, determined by the thickness of a material layer or layers in which the nanopore is formed, impacts the nature of molecular traversal of the nanopore, and directly limits the sensitivity and the resolution with which molecules in the nanopore can be detected and analyzed.